Matrix metalloproteinases (MMP) are a family of zinc-containing calcium dependent proteinases, including stromelysins, collagenases, and gelatinases. These MMP enzymes are capable of degrading the proteinaceous components of connective tissue and appear to be involved in tissue remodeling, i.e., wound healing and connective tissue turnover. Approximately thirteen MMPs have been identified. The collagenases cleave fibrillar collagen. The stromelysins degrade fibronectin, laminin, and proteoglycans in addition to collagen. The gelatinases can degrade denatured collagen (gelatin) and type IV collagen, the major component of basement membranes.
Elevated levels of collagenase and stromelysin are associated with both osteo- and rheumatoid arthritis, having been observed both in synovium and cartilage in amounts proportional to the severity of the disease. The gelatinases are thought to play a key role in tumor metastasis, since they degrade the basement membrane through which tumor cells must pass in order to migrate away from the primary tumor site and thus enable the migration from the primary site. Gelatinase is also associated with the process of angiogenesis which is essential for the growth of solid tumors. In addition to the association with osteo- and rheumatoid arthritis and tumor metastasis, MMPs are implicated in corneal ulceration, gingivitis, multiple sclerosis and other neurological disorders, and emphysema (Beeley et al., Curr. Opin. Ther. Patents 4(1), 7-16 (1994)).
Compounds which bind zinc at the active site of the enzyme prevent the catalytic activity of MMPs. MMP inhibitor activity has been found in certain peptidyl hydroxamic acids, peptidylalkyl carboxylic acids, peptidylphosphinic and phosphonic acids. Furthermore, peptidyl thiols incorporating a carbonyl group two atoms removed from the thiol group have been shown to be potent MMP inhibitors. For example, in the compound below, as disclosed in Journal of Medicinal Chemistry 36, 4030-4039 (1993), the SSR ##STR2## isomer is a potent (IC.sub.50 =2 nM) inhibitor of human collagenase (J. R. Morphy et al., Current Medicinal Chemistry 2,743-762 (1995).
Merck discloses the compound ##STR3## in the PCT application WO 9407481 as a moderate inhibitor of the MMP stromelysin. The compound ##STR4## is disclosed in the PCT application WO 9513289. The mercapto sulfide MMP inhibitor compound below was disclosed in the PCT application WO 9509833. ##STR5## MMP inhibiting compounds of the formula ##STR6## where P is H, methyl or phenyl are disclosed by Donald et al., U.S. Pat. No. 4,595,700. The compound where P is 2-oxopropyl is approximately 20 times more potent than the compound where P is methyl which is in turn about 20 times more potent than the compound where P is hydrogen (EP 0322,184 A2). In all of the above noted examples the thiol moiety is two carbons removed from an amides carbonyl group.